Article V explains the process for amending the Constitution. An amendment is like a PS; it's something that the Founders forgot to say. Examples of things they forgot to say include: gay love is sin, abortion is murder, and flag-burning should be punishable by death.
Article VI says that no religious test should be required as a qualification for public office. Isn't that marvelous? In practice, this means that Christians never have to take a test to prove they believe in Jesus; that Jews get the benefit of the doubt because they're on the road to being perfected as Christians; and that Muslims have to swear on the Koran that they're not terrorists.